Maybe that goes for parents and spouses as well, but I claim much less expertise in those areas.
If you've the good fortune of a client or potential client giving you a part of his business day because you've convinced him you that believe that you can and would like to help him, what's the message he receives when your cell rings or you check for new messages, across the desk from him. (If you are one of, sadly, the minority of folk out to dinner with the wife and kids and no cell phone in sight on your table, what's your reaction to the guy at the next table celling-away?)
You client deserves your complete and thoughtful attention. You are there intruding on his schedule for his benefit. You are his samurai--at his service--you exist for his well-being, at least for the hour he's given you.
Absent a personal crisis which you must be able to respond to quickly, everything else can and should wait.
Leaving your cell phone in the glove compartment may be harder than stopping smoking, but you can do it. I know you can!
Love Your Work and Work Tirelessly
Communicate Honestly and Fearlessly
Serve, Don't Sell